Recording paper for spark recorders



y 1958 w. H. e. BAUMLEIN 2,833,677

RECORDING PAPERFOR SPARK RECORDERS Filed June 7. 1955 Fly. 2

United. states RECORDING PAPER FDR SPARK REQORDERS Wilhelm Hermann Gunther Eaumlein, Gcrnsbach, Baden, Germany, assignor to Sch-oeller & Hoesch, Gernshacli, Baden, West-Germany This invention relates to record paper for use in apparatus of the kind in which writing designs and other intelligence is marked on paper by means of an electric spark.

It is therefore an object of the invention to provide a record paper in which a paper backing is electrically conductive and an insulating layer is interposed between the metal layer and the paper. in such a record paper the conductive backing acts as counter electrode for the marking electrode and the current is supplied, if desired but not necessarily, by providing a metal support, for example a drum at the place of marking. The metal layer fulfills no electrical function but acts only as combustion material for the sparks. Therefore it does not need to have high conductivity and it may consist of discrete metal particles, the particle size and density of distribution corresponding to the solvent power of the record. The advantage of the use of the metal. layer as a mark creating medium consists in the high heat absorption coefficient, the local overheating at only momentary heating and thereby making possible a sharp and quick marking with substantially weaker spark energy.

The insulating intermediate layer avoids the disadvantages of known record paper regarding action between the metal layer and the counter electrode. In the record paper according to the invention the sparks traverse the space between the spark or marking electrode and the counter electrode always along the shortest path, that is vertically to the paper and not wandering laterally since their point of contact imparted on the counter electrode remains conductive. Thus even at slow speed of paper travel there is a sharp marking track whereby the spark heat in the metal particles in the spark path is scattered in the insulating layer and the paper backing layer.

As compared with known record paper with conductive paper backing layer and electrolytically sensitive covering layer, the metal coated record paper of this invention differs in that the marking is facilitated by the absence of moisture in the spark developing layer whereby the capacity for sorting and use of the record paper is improved. The new record paper differs from known metallized condenser paper with a filling varnish layer for the uneven ness in the paper backing which cannot be present in condenser paper, apart from the dilferent purpose to be served.

Instead of paper, other sheet material for example plastics, fabrics, etc. may be used to which the necessary electric conductivity has been imparted by impregnation or addition of. the material.

The paper backing may be made by known paper making methods. Preferably there should be added to the paper mass in the hollander finely divided carbon, for example soot or lampblack. Also finely divided metals and preferably oxidation preventing additions such as high atent O Patented May 6, 1958 molecular carbohydrates may be added to the paper mass and if desired also dark colored dyes or pigments.

The insulating intermediate layer is preferably made from a viscous solution of a cellulose derivative, and artificial materials, for example acetylcellulose of the linear polymer type. The varnish may have dyes or pigments embodied therein in order to increase the optical contrast against the metal layer at the marking track.

The metal layer may be formed in various known Ways, for example spraying by compressed air (the Schoop method), thermal vaporizing, cathonic spraying and thermal decomposition, for example of carbonyls, acetylene acetones, etc.

The metal used may be light colored as zinc, aluminum and nickel, deposited on a dark colored base or binding. It is also possible to use a colored metal such as copper, bronze, etc. with a complementary colored backing, for example with a greenish or bluish color.

The drawing shows two embodiments of the invention enlarged scale in which Figures 1 and 2 are cross sections of the record paper.

The record paper of Fig. 1 consists of a paper backing layer 1 made of equal parts by weight of paper pulp and soot along with conventional sizing agents as known in the art. it is coated on one side with a colorless layer 2; of acetylcellulose which serves as insulator and to smooth out the paper irregularities. On this intermediate layer 2 is a thin skin layer about I'LL thick of metal 3, for example nickel formed by blowing or projecting nickel carbonyl vapor and then decomposing it by heat.

in the record paper of Fig. 2 the paper backing 1' also consists of soot containing pulp. The intermediate layer 2 consists of polystyrol varnish containing a white pigment such as titanium oxide. The record producing metal layer 3 consists of copper deposited by decomposition of copper acetic acetone.

The record paper of this invention is used in natural air dried condition with the metal layer moving opposite the spark electrode of the printing device.

The marking track is produced by a sharp edge burning oil or vaporization of the metal layer lying in the path of the sparks and is easily perceptible owing to contrast between the exposed paper backing and the undisturbed metal layer. The air resistance of the metal layer is unlimited but if desired the printing can be fixed by spraying thcreover a varnish layer or other fixing medium.

I claim as my invention:

1. A multi-layer recording paper for use in spark recording by printing intelligence by electrically burning away a metal coating, comprising a basic paper layer which is conductive, a metallic top layer having a low electric conductance across its plane, and a uniform and continuous dielectric layer interposed between the two layers and throughout electrically separating said basic layer and said top layer.

2. A multi-layer recording paper according to claim 1, in which said insulating layer contains a substance contrasting in color from said top layer.

3. A multi-layer recording paper according to claim 1, in which said top layer consists of a nickel deposit.

References Cited in the file of this patent UNITED STATES PATENTS 2,310,946 Finch Feb. 16, 1943 2,471,607 Calhin May 31, 1949 2,687,361 Traub Aug. 24, 1954- 2,726,l68 Roddin et a1. Dec. 6, 1955 2,726,179 Ortlieb et al. Dec. 6, 1955 

1. A MULTI-LAYER RECORDING PAPER FOR USE IN SPARK RECORDING BY PRINTING INTELLIGENCE BY ELECTRICALLY BURNING AWAY A METAL COATING, COMPRISING A BASIC PAPER LAYER WHICH IS CONDUCTIVE, A METALLIC TOP LAYER HAVING A LOW ELECTRIC CONDUCTANCE ACROSS ITS PLANE, AND A UNIFORM AND CONTINUOUS DIELECTRIC LAYER INTERPOSED BETWEEN THE TWO LAYERS AND THROUGHOUT ELECTRICALLY SEPARATING SAID BASIC LAYER AND SAID TOP LAYER. 